spyder bodies are interchangable with the only thing needed to be swapped is the bolt. If you bought that body the only thing you would need is a long rear cocking bolt and you'd be all set. I think I have a stock black one if you are interested

Yes, all Spyder parts are interchangeable except the bolts..like the difference in top-cocking and rear-cocking like he said. And if you were to get into the older Spyder bodies, you'd run into striker/sear compatibility problems but as long as the Spyders are recent you're fine. If you want the Gothic body, just buy either tib's bolt or an ACS bolt and swap all your parts over from your Imagine to the Gothic body and you're set.